Induction of electrophile-responsive element (EpRE)-mediated gene expression by tomato extracts in vitro

Combining an in vitro reporter gene assay with metabolomics to identify tomato phytochemicals responsible for inducing electrophile-responsive element (EpRE)-mediated gene transcription

“…Tomato samples were enzymatically hydrolysed as described previously (Gijsbers et al 2012). In short, 500 ll 0.1 M sodium acetate (pH 4.8) and 167 ll Viscozyme L solution (Sigma-Aldrich) were added per gram of blended tomato fruit.…”

“…Out of the 313 metabolites, 64 (20 %) were selected to be most different between the two groups based on two criteria: (1) a p \ 0.01 between the two accession groups in a two sided Student's t test and (2) the average intensity within the two accession groups was at least tenfold different. These 64 metabolites included nine putatively annotated flavonoids, among which were the aglycones of quercetin and kaempferol (p = 0.0001 and 0.0003, respectively) which have previously been shown to be able to induce EpRE-mediated gene expression as pure compounds (Gijsbers et al 2012;Lee-Hilz et al 2006). Tricaffeoylquinic acid also showed a significant (p = 0.0001) difference between the two groups.…”

“…Health-dedicated cell-based assays might provide a relatively fast and low cost method to screen crude extracts of tomato for their ability to induce health-beneficial genes (Gijsbers et al 2012(Gijsbers et al , 2013. These assays make use of human or animal cell lines that have been stably transfected with a health-beneficial pathway-specific response element coupled to a luciferase (LUX) reporter gene, which can be used as an easy measurable marker for the induction of health-beneficial genes/response pathways in human and/or animal systems.…”

“…Previously Gijsbers et al (2012) developed a method to test different solvent extracts from tomato for their ability to induce EpRE-mediated gene expression, using an EpRE-LUX reporter cell line. They showed that neither chloroform extracts, containing tocopherols and carotenoids, like lycopene, nor aqueous-methanol extracts, containing semipolar metabolites like glycosylated flavonoids and alkaloids, from tomato fruit were able to induce EpRE-controlled luciferase expression.…”

“…They showed that neither chloroform extracts, containing tocopherols and carotenoids, like lycopene, nor aqueous-methanol extracts, containing semipolar metabolites like glycosylated flavonoids and alkaloids, from tomato fruit were able to induce EpRE-controlled luciferase expression. However, aqueous-methanol extracts of glycosidase treated tomato fruits, obtained using a fungal glycosidase which mimics the action of intestinal glycosidases such as lactase-phloridzin-hydrolase (LPH) and cytosolic b-glucosidase (CBG) (Day et al 1998), were able to activate EpRE-mediated luciferace expression (Gijsbers et al 2012). Considering these previous findings with glycosidase treated and non glycosidase treated tomato fruit, in addition to the fact that most if not all glycosides will be hydrolyzed in the human intestine (Hollman et al 2011), it is thus concluded that a deglycosidation step is key in the EpRE-LUX activity assay.…”